Blank rails 4.1.5 app (using rails-api)

Command:

```
rails-api new publishing-api --skip-action-view --skip-sprockets \
                             --skip-javascript --skip-test-unit
```
Consolidate README files in to a single Markdown file
Remove some Rails cruft

We don't need these things for this application.
Pin gem versions

As per:
https://github.com/alphagov/styleguides/blob/f88150845037cae27f5c23d666e43f1081fc96f7/ruby.md#gemfile
Setup RSpec

We'll be using this for testing the application.
Rename `test.sh` to `jenkins.sh` to be consistent with other apps
Rename `test_branches.sh` to `jenkins_branches.sh`

Be consistent with other applications.
Add simplecov for test coverage reports
Add a minimal healthcheck path

This is our monitoring endpoint for the application.
Add logstasher for logstash-friendly logging
Setup airbrake

We'll use this to forward on exceptions when in our full environments.
Add unicorn as a dependency

We'll be using this as our server to run the application.
Use latest version of Rails (4.1.8)

The `rails-api` gem uses whatever the latest version of `rails` you
have installed instead of using the latest upstream version.

(The application skeleton was initiated with `rails-api`)
Disable loading of ActiveRecord

It won't be needed for this application.
Disable loading of ActiveModel

It's not necessary for this application.
Enable all suggested defaults for RSpec
Merge pull request #1 from alphagov/setup-publishing-api-app

Setup minimal working Rails application